Some sitcoms are born fully formed, but that wasn’t the case with Happy Days. Though it debuted as a mid-season replacement in January 1974 and finished in the #16 spot that season, it took a second year before the series really hit its stride. By Season 4, Happy Days had become a pop phenomenon, in part because the ‘70s were a time of turmoil and this show transported everyone back to the happier, simpler 1950s. But a “greaser” named Arthur “Fonzie” Fonzarelli (Henry Winkler) quickly became the show’s most popular, and his catch phrase “Heyyyy!” caught on just as much as the show’s “Sit on it!” insult.

During its fourth season Happy Days became the #1 show in America, then dropped to #2 its fifth season and #3 its sixth. But truthfully, the numbers don’t tell the whole story. The early shows were driven by ‘50s nostalgia and ‘50s situations and phrases, like “You got it made in the shade.” Then the show’s success changed everything. Fans loved Fonzie, so, as it happened with Mister Ed and other TV sitcoms where a character took over, more episodes were written to showcase him. And when fans responded well to the crooning of Potsie Weber (Anson Williams), he got more songs—way too many, given the generic quality of his voice. Before you knew it, the plots bore little resemblance to the 1950s and were instead character-driven. That also meant the plots became more generic, because, no longer tied to the ‘50s, they could have happened to anyone.

In Season 5 Fonzie “jumped the shark,” literally, on water skis. But figuratively the phrase has come to mean when a TV show starts to go downhill. You don’t have to look any farther in Season 6 than the first three episodes, in which the whole cast packs up and moves west to help Marion’s uncle save his dude ranch. It’s clear that the writers thought the characters were so popular that they could put just about anything down on paper and it would work. But with such character-driven plots, ‘50s nostalgia was the first casualty . . . and that’s what had made the show popular in the first place. This season, the characters—including Ralph Malph (Donnie Most), Mrs. C. (Marion Ross), Mr. C. (Tom Bosley), and Al from the drive-in (Al Delvecchio) seem like caricatures of themselves.

A full 25 out of 27 Season 6 episodes are inferior, with the only exceptions being one in which Potsie drops out of school, and another in which Joanie (Erin Moran) falls for the high school quarterback but sees him with another girl and ends up facing her Sweet Sixteenth birthday party without a date—and even that episode is marred by Potsie’s singing. The other shows involve an incredible amount of silliness and hard-to-believe situations, whether its Fonzie becoming blind after being hit by a serving tray, the gang dressing up for Thanksgiving, or Richie falsely accused of being the Kissing Bandit. These “post-shark” episodes seem mostly contrived, and if families want to give Happy Days a chance, your best bet is to go with Seasons 2, 3 and 4. Those are truly family-friendly seasons that hold up, still.